Gitaroo Man initially had a very low print run and was in high demand thus driving the price up…

about 2 years ago, it got reprinted and was readily available though the price was still up there… Game Stop was selling used copies for $39.99 at that time and today I believe that it sells used for $24.99

Gitaroo Man has also been ported to the PSP.

Its a really great game. Not only does it require precise, rhythmic button presses but also timely and agile use of the analog control. IIDX and Gitaroo Man are the games that got me into music games… Honestly, if Guitar Freaks had better music, I'd favor that over the western music games… Bemani games are pretty well done I guess but IIDX is the only one I really get into… my wife owns in IIDX - she make me look horrible… she also gets into DDR and In the Groove.

Then why has nobody in this thread heard of it, and why didn't it make the greatest hits collection?

Mathius

I cannot know why one has or hasn't heard of a specific game…
Regarding Gitaroo Man, it wasn't a triple A title which is why it was rare for a long time… case of short supply, high demand, for a game people wanted to play and were willing to pay for it.

Games that are released in a "greatest hits" packaging are for the most part Triple A titles a a budget price. Many games sell well and never get repacked as such. Sometimes on purpose to maintain price point…